Heretofore, for example, in an automated assembly line for automobiles, an assembly process has been carried out in which clamping is performed by a clamp apparatus under a condition in which pre-formed frames are positioned in an overlaid manner and the frames are welded together.
As one clamp apparatus of this type, for example, as disclosed in Japanese Patent No. 4950123, the clamp apparatus comprises a pair of clamp arms, the clamp arms being disposed on left and right sides, respectively, and the clamp arms are disposed rotatably through respective pins. Proximal ends of the clamp arms are supported pivotally through a base that is connected to a drive unit, such that distal ends of the clamp arms can be operated to open and close. A workpiece such as a frame or the like can be gripped from left and right sides thereof by the distal ends of the pair of clamp arms.